1. Field of the Invention
The present invention relates generally to method of controlling an automatic transmission and more specifically to a method of controlling a continuously variable transmission which induces optimal performance therein.
2. Description of the Prior Art
In a previously proposed continuously variable transmission of the type utilizing a V belt and continuously variable diameter sheaves (such as disclosed in Japanese Patent Application Provisional Publication No. Sho 57-90450 and more specifically in European Patent Publication No. 00 73 475a2 published on Mar. 9, 1983), the gear ratio is varied by computing the difference between a desired or target gear ratio and the actual ratio and operating a control device such a motor or the like, in a manner to reduce the difference. This motor has been set ot reduce the difference at the same relatively high rate, irrespective of the actual ratio of the transmission and as long as the difference exists, so as to endow good response characteristics on the arrangement. However, in case the pairs of frusto-conical cones defining each sheave are hydraulically linked with the above mentioned motor, a problem has been encountered in that pressure in the sheave control chamber being depressurized, tends to drop too rapidly allowing the V belt to slip undesirably.
This of course lowers the working life of the belt notably.
The disclosure of the above mentioned documents relating to the mechanical and hydraulic components thereof, is herein incorporated by reference thereto.